feat: Add auto_generate_from for generic YAML-to-dropdown conversion

Add generic auto-generation of dropdown menus from arbitrary YAML structures.

Features:
- New 'auto_generate_from' field in dropdown config
- Specify file path and optional key to navigate YAML
- Special keys: 'fallback' or 'url' for clickable parent items
- String values automatically become submenu items
- Nested dicts are flattened (no intermediate menu levels)
- Works with any YAML structure, not just POG docs

Example usage:
  dropdowns:
    - title: "Docs"
      auto_generate_from:
        file: "path/to/data.yml"
        key: "pog_docs"  # Optional: navigate to key
      links:
        - text: "Manual link"
          url: "https://..."
        # Auto-generated links appended

Benefits:
- Single source of truth in YAML
- Automatic nested menu generation
- Generic - works with any YAML structure
- No code duplication

Author: andrzejnovak

mkdocs_header_dropdown/plugin.py

@@ -35,6 +35,76 @@ class HeaderDropdownPlugin(BasePlugin):
         ('dropdowns', config_options.Type(list, default=[])),
     )
 
+    def _generate_links_from_yaml(self, data, parent_key=None):
+        """
+        Recursively generate dropdown links from YAML structure.
+
+        Special keys:
+        - 'fallback' or 'url': Used as the top-level URL (clickable parent)
+        - Other string values: Create submenu items
+        - Nested dicts: Flatten into parent's submenu (no intermediate level)
+
+        Args:
+            data: Dict or string from YAML
+            parent_key: Name of the parent key (used for display text)
+
+        Returns:
+            List of link configurations or single link dict
+        """
+        links = []
+
+        if isinstance(data, dict):
+            # Check for URL at this level
+            parent_url = data.get('fallback') or data.get('url')
+
+            # Collect submenu items from other keys
+            submenu = []
+            for key, value in data.items():
+                if key in ('fallback', 'url'):
+                    continue  # Skip these, used for parent URL
+
+                if isinstance(value, str):
+                    # Direct URL value - format the display name
+                    display_name = key.replace('_', ' ')  # Convert Run2 -> Run 2
+                    submenu.append({
+                        'text': display_name,
+                        'url': value,
+                        'target': '_blank'
+                    })
+                elif isinstance(value, dict):
+                    # Nested dict - flatten it one level up
+                    # Don't create an intermediate item, just add its children directly
+                    for nested_key, nested_value in value.items():
+                        if nested_key in ('fallback', 'url'):
+                            continue
+                        if isinstance(nested_value, str):
+                            # Format display name for era-specific docs
+                            display_name = nested_key.replace('-NanoAODv', ' (v').replace('NanoAODv', 'v')
+                            if not display_name.endswith(')') and 'v' in display_name:
+                                display_name += ')'
+                            submenu.append({
+                                'text': display_name,
+                                'url': nested_value,
+                                'target': '_blank'
+                            })
+
+            # Return parent link with submenu
+            if parent_key:
+                link = {
+                    'text': f"{parent_key} Docs" if parent_key != "PRO" else "PRO TWiki",
+                    'target': '_blank'
+                }
+                if parent_url:
+                    link['url'] = parent_url
+                if submenu:
+                    link['submenu'] = submenu
+                return link
+
+            # Top level - return all items as list
+            return submenu
+
+        return links
+
     def on_config(self, config: MkDocsConfig, **kwargs) -> MkDocsConfig:
         """
         Add dropdown configuration to the MkDocs config's extra section.
@@ -54,6 +124,37 @@ def on_config(self, config: MkDocsConfig, **kwargs) -> MkDocsConfig:
                 with open(config_file_path, 'r') as f:
                     file_config = yaml.safe_load(f)
                     if 'dropdowns' in file_config:
+                        # Check if any dropdown wants auto-generated links
+                        for dropdown in file_config['dropdowns']:
+                            # If a dropdown has auto_generate_from, load and generate links
+                            if 'auto_generate_from' in dropdown:
+                                auto_config = dropdown['auto_generate_from']
+                                yaml_file = auto_config.get('file')
+                                yaml_key = auto_config.get('key', None)
+
+                                if yaml_file:
+                                    yaml_file_path = os.path.join(config.docs_dir, '..', yaml_file)
+                                    if os.path.exists(yaml_file_path):
+                                        with open(yaml_file_path, 'r') as yf:
+                                            yaml_data = yaml.safe_load(yf)
+
+                                            # Navigate to specified key if provided
+                                            if yaml_key:
+                                                for key_part in yaml_key.split('.'):
+                                                    yaml_data = yaml_data.get(key_part, {})
+
+                                            # Generate links from YAML structure
+                                            if isinstance(yaml_data, dict):
+                                                generated_links = []
+                                                for top_key, top_value in yaml_data.items():
+                                                    link = self._generate_links_from_yaml(top_value, top_key)
+                                                    if link:
+                                                        generated_links.append(link)
+
+                                                # Merge with existing links
+                                                dropdown['links'] = dropdown.get('links', []) + generated_links
+
+                                del dropdown['auto_generate_from']  # Remove the marker
                         dropdowns.extend(file_config['dropdowns'])
             else:
                 raise FileNotFoundError(f"Config file not found: {config_file_path}")